Innate Immunity plays a fundamental role in atherogenesis and our work has provided an improved understanding of this by demonstrating that oxidation-specific epitopes (OSE), which are generated on oxidatively damaged molecular complexes, such as OxLDL and apoptotic cells, are major targets of innate pattern recognition receptors, such as lgM Natural Antibodies (NAbs). During the first cycle, we demonstrated that 20-30% of all lgM NAbs bind to OSE in both mice and humans, and we proposed that lgM OSE-NAbs have been conserved to provide homeostasis to the many OSE generated in both health and disease. Considerable data support an atheroprotective role for lgM in murine models and lgM titers in humans are inversely related to cardiovascular disease (CVD). In the renewal, we will focus on understanding the role of NAbs in mice and humans, and define the mechanisms that regulate 8-1 cells that generate NAbs. Specific Aim 1 will define the repertoire and prevalence of OSE NAbs in mice and humans. We will generate a B-1 cell derived database of lgM NAb heavy chain variable (IGHV) CDR3 sequences and their relative expression in both humans and mice. We will then sort OSE-B-1 cells to annotate OSE NAbs, and will examine their relative expression under experimental models of inflammation and atherosclerosis in mice, and in epidemiological studies in humans. Specific Aim 2 will define the roles of OSE NAbs and B-1 cells in inflammation and atherogenesis. Using transgenic mice expressing OSE antibodies, we will seek to define the mechanisms by which OSE-Abs influence inflammation and atherosclerosis. Because these NAbs target prevalent oxidized lipids in atherosclerotic lesions, these studies should define the importance of these oxidized moieties in mediating inflammation and atherogenesis. Specific aim 3 will test the hypothesis that vital functions of B-1 cells, such as proliferation and secretion of NAbs are positively regulated by TLRs, while the nuclear receptors GRand LXR negatively regulate B-1 cells. We will determine the impact of these immune modulators on transcriptional regulation of B-1 cells in comparison to B-2 cells and macrophages, to provide an improved understanding of the integrated responses to these immune cell regulators. These studies should yield new insights into the important role that innate immunity plays in inflammation and atherosclerosis, and may lead to novel diagnostic and therapeutic approaches for CVD.